asp.net+ Ext.Ajax.request 缓存有关问题

asp.net+ Ext.Ajax.request 缓存问题
Ext.Ajax.request({
url: '/AJAXRequest/Login.aspx',
params: 'userType=0&userName="vvjob2008"&r='+Math.random(),
method: 'POST',
success: this.LoginSuccess,
failure: this.LoginFailure,
disableCaching: true
});

我在 Page_Load 加了以下代码也没办法清除缓存

Response.Charset = "UTF-8";
Response.Buffer = true;
Response.ExpiresAbsolute = DateTime.Now.AddDays(-1.0);
Response.Expires = 0;
Response.CacheControl = "no-cache";
Response.AddHeader("Pragma", "No-Cache");

请各位帮忙指点一下!!!